Interpolation for degree angles

Interpolation for degree angles

Usage

approx_degrees(
  h1,
  h2,
  h = NULL,
  preset = "custom",
  direction = NULL,
  digits = 10,
  verbose = FALSE,
  ...
)

Arguments

h1

numeric vector of degree angles, which should represent the "degree angles from".

h2

numeric vector of degree angles, which should represent the "degree angles to".

h

numeric or NULL, where a numeric vector is a vector of degree angles "from" that should be converted to the corresponding interpolated angle "to", When h is NULL then the object returned is a function to be called to convert a numeric vector "from" to degree angles "to".

direction

integer or default NULL, which detects the direction using the input data. The direction represents whether h1 and h2 are both increasiing together, which is direction=1. When h1 is increasing by h2 is decreasing, direction=-1.

digits

integer value indicating the number of digits of precision to use for the input h1 and h2 degree angles, used when confining to 360 degrees with h1 %% 360, and this step sometimes produces slight variations for equivalent values. For example ((12.2 %% 360) == (372.2 %% 360)) is not TRUE without rounding to 13 or fewer digits.

verbose

logical indicating whether to print verbose output.

...

additional arguments are ignored.

Details

This function is analogous to stats::approx() except for the special case of degree angles. In this case, degrees are confined to the range [0, 360], and angle are smoothly interpolated around the degrees of a circle.

This function should work properly even when the degree angles in h2 are reversed, or offset. The only implicit requirement is that angles in "from" should be mapped to one and only one angle in "to".

See also

Other colorjam hue warp: add_colorjam_preset(), add_colorjam_step(), adjust_hue_warp(), colorjam_presets(), colorjam_steps(), display_degrees(), h2hw(), h2hwOptions(), hcl_to_hsl_hue(), hsl_to_hcl_hue(), hw2h(), mean_angle(), plot_colorjam_preset(), plot_colorjam_steps(), remap_colorjam_preset(), validate_colorjam_preset()

Examples

h_colors <- jamba::getColorRamp(c("white", "firebrick"), n=35, trimRamp=c(1, 0));

h1 <- c(12.2, 27.3, 47.0, 66.5, 85.9, 106.3, 131.7,
   223.1, 263.2, 277.2, 307.7, 345.3, 372.2)
h2 <- seq(from=0, to=360, length.out=13)
h_from <- seq(from=0, to=360, length.out=36)[-36]
h_to <- approx_degrees(h1, h2, h_from)
withr::with_par(list("mfrow"=c(2, 2)), {
display_degrees(h_from, col=h_colors)
display_degrees(h_to, col=h_colors)
plot(h1, h2, pch=20, col="#55555555", type="l",
   main="Input h1,h2")
points(h1, h2, pch=20, col=h_colors)
plot(h_from, h_to, pch=20, col="#55555555", type="l",
   main="Output approx_degrees()")
points(h_from, h_to, pch=20, col=h_colors)
})


h1 <- c(12.2, 27.3, 47.0, 66.5, 85.9, 106.3, 131.7,
   223.1, 263.2, 277.2, 307.7, 345.3, 372.2)
h2 <- rev((seq(from=0, to=360, length.out=13))[c(9:12,1:9)])
h_from <- seq(from=0, to=360, length.out=36)[-36]
h_to <- approx_degrees(h1, h2, h_from, direction=-1)
h_to <- approx_degrees(h1, h2, h_from)
withr::with_par(list("mfrow"=c(2, 2)), {
display_degrees(h_from, col=h_colors)
display_degrees(h_to, col=h_colors)
plot(h1, h2, pch=20, col="#55555555", type="l",
   main="Input h1,h2")
points(h1, h2, pch=20, col=h_colors)
plot(h_from, h_to, pch=20, col="#55555555", type="l",
   main="Output approx_degrees()")
points(h_from, h_to, pch=20, col=h_colors)
})


# apply no transform
approx_degrees(h1=0, h2=0, h=c(0, 90, 180, 270))
#> [1]   0  90 180 270

# apply 180 degree transform
approx_degrees(h1=0, h2=180, h=c(0, 90, 180, 270))
#> [1] 180 270   0  90
approx_degrees(h1=180, h2=0, h=c(0, 90, 180, 270))
#> [1] 180 270   0  90

# flip the direction
approx_degrees(h1=c(1, 360), h2=c(359, 0),
   h=c(0, 90, 180, 270))
#> [1]   0 270 180  90
approx_degrees(h1=c(1, 360), h2=c(359, 0)+90,
   h=c(0, 90, 180, 270))
#> [1]  90   0 270 180
approx_degrees(h1=c(1, 360)+90, h2=c(359, 0),
   h=c(0, 90, 180, 270))
#> [1]  90   0 270 180

# verify reverse h2 with break across 0-360
seq1 <- seq(from=0, to=330, by=30)
seq2 <- (rev(seq1) + 120) %% 360
seq_out <- seq(from=0, to=350, by=10);
approx_out <- approx_degrees(h1=seq1, h2=seq2, h=seq_out)
plot(seq1, seq2, pch=20, col="blue", asp=1, ylim=c(0, 360))
points(seq_out, approx_out, col="red", cex=2)


# verify forward h2 with break across 0-360
seq1 <- seq(from=0, to=330, by=30)
seq2 <- (seq1 + 120) %% 360
seq_out <- seq(from=0, to=350, by=10);
approx_out <- approx_degrees(h1=seq1, h2=seq2, h=seq_out)
plot(seq1, seq2, pch=20, col="blue", asp=1, ylim=c(0, 360))
points(seq_out, approx_out, col="red", cex=2)